But yesterday, a spokesman for Mr Abetz told Fairfax Media the Minister has recently "received a complaint which will be dealt in due course".

Mr Abetz said the complaint would be subject to "due process".

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"Well, I'm going to go through this step by step, and come to a determination in due course. Whether or not any action needs to be taken and, if so, by whom," Mr Abetz told conservative commentator Andrew Bolt on Sunday.

"As you might imagine, I don't get to sight the medical certificates that may or may not have been tendered by Mr Lawler, so I'm not going to get into the detail of the matter."

Mr Lawler has publicly supported and legally represented his partner, embattled former Health Services Union leader Kathy Jackson, during her Federal Court appearances over allegations she rorted $1.4 million from the union.

During her appearances before the Royal Commission into Trade Union Governance and Corruption, Ms Jackson was unable to provide any records of large cash withdrawals.

Asked why large sums of money ranging from $3500 to $50,000 had been withdrawn from a slush fund account which only she could access, Ms Jackson said she had no recollection of what a number of withdrawals were spent on because her only records were kept in an exercise book which had gone missing.

In 2002 under the Howard government, Tony Abbott appointed Mr Lawler to the Industrial Relations Commission, the predecessor to the Fair Work Commission. Mr Lawler can only be removed by agreement between both houses of Federal parliament.

The Fair Work Commission is powerless to sack Mr Lawler and the Fair Work Act is silent on the issue of his sick leave entitlements.

Fair Work Commission president Iain Ross has declined to comment on Sunday, but the President of the Australian Bar Association, Fiona McLeod, has defended him against criticism for his failure to act.

"The President of the Fair Work Commission does not have the power to remove a member of the Commission - that is properly only a power of the Parliament," Ms McLeod said.

"It is a matter for the Parliament as to whether it wishes to consider legislative amendments to the Fair Work Act to deal with the current vacuum in the legislation."

Opposition spokesman for Employment Brendan O'Connor said "it is incumbent" upon Prime Minister Tony Abbott and Senator Abetz to examine Mr Lawler's conduct in response to questions about his duties as an officer of the Commission.

"If the government fails to act, there is a growing concern that the reputation of the Fair Work Commission will be called into question and result in a potential loss of public confidence," Mr O'Connor said.

ACTU president Ged Kearney said there are minimum safety net provisions, but entitlements including sick leave can vary between workplaces depending on the agreement reached between the employer and employees.

Asked whether many workers would be entitled to nine months of sick leave, Ms Kearney said the ACTU's role "is to maintain and improve the minimum safety net protections for all Australian workers rather than comment on specific agreements".